The present invention relates to a method of treatment of a metal object to provide it with biocidal properties. In particular but not exclusively, the invention relates to treated metal objects that provide a reduced risk of irritation or infection when the object is in contact with a body.
Metal materials come into contact with the body in numerous situations, for example in surgery, where implants are used, these implants being inserted into the tissue of the body, be this soft or hard tissue. In the case of cancer treatment of the bone for example, cancerous bone tissue is removed, and a prosthetic metal implant is used to replace that part of the bone that has been removed. Implants are also used for partial or full replacement of bones in joints (e.g. hips) and also in other fields such as dentistry and maxillofacial surgery. Implants and medical devices may also be used in cases of amputation or trauma and such devices may be percutaneous of transcutaneous. Implants for the foregoing (and other) uses may be of titanium metal or titanium alloy. Titanium metal and titanium alloys are biocompatible, relatively strong and relatively light.
Further, metal comes into contact with the body in the case of jewellery. Much jewellery is made from metal alloys, but these may contain components that react with moisture in perspiration. Also, pitting of the metal alloy can occur due to the presence of chloride ions in the perspiration and this can create a seat for bacteria to accumulate which can then result in skin infections if the metal alloy comes into contact with broken skin. Irritation and infection can occur not only for jewellery that pierces the body but also for jewellery that sits next to the skin if the wearer has sensitive skin.
As can be seen, in both the medical and jewellery fields, the use of metal which comes into contact with body tissue runs the risk of introducing infection, or infection occurring. In both areas it has been suggested that metallic silver might be electroplated onto metal. Silver is known to have biocidal properties and the silver controls infection without causing toxic effects to the subject. However such coatings may be undercut due to corrosion from body fluids, so that the coating may detach from the metal, which may lead to increased wear and cause tissue damage from detached particles containing silver.